JP2003133037A - Induction heating method and device for metal band plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for induction-heating a metal band plate in a predetermined pattern in its widthwise direction regardless of a carrying speed of the metal band plate. SOLUTION: The induction heating is carried out by sequentially disposing rhombic coils 2a and elliptic coils 2b having heating patterns different from each other along the carrying direction of the metal band plate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for inductively heating a metal strip, and more particularly to a technique for heating a metal strip in a desired heating pattern independent of its transport speed.

[0002]

2. Description of the Related Art Conventionally, various heating methods such as roll heating and infrared heating have been used for heating a metal strip plate which is a strip-shaped metal base material. In particular, in heating when laminating a metal strip such as aluminum with a resin film,
It prevents metal powder or the like of the metal strip itself from being generated and attached at the time of contact with the heating roll, and prevents the metal powder from mixing between the base material and the resin film at the time of laminating, and the metal strip by heating. It is necessary to suppress the decrease in the strength of. A high-frequency induction heating method capable of heating a metal strip in a non-contact manner in a short time is known as a heating method satisfying such requirements.

By the way, if the metal strip cannot be heated to a uniform temperature in the width direction, the metal strip is bent and may come into contact with a member such as a coil during transportation. Further, for example, when laminating the resin film, the laminating may be incomplete. Therefore, in the conventional induction heating device for a metal strip, various measures are taken in the shape of the single coil and the magnetic flux distribution in order to uniformly heat the metal strip in the width direction.

For example, the inventor of the present application discloses Japanese Patent Application 2
000-338228, a rhomboid coil in which both ends of the long axis are curved is proposed. And according to this technique, the heating range is adjusted according to the width of the metal strip by changing the inclination angle of the long axis of the coil with respect to the width direction of the metal strip, and the uniform heating of the metal strip is realized. ing.

[0005]

By the way, in the case of performing induction heating using a single coil, in order to obtain a uniform heating pattern in the width direction of the metal strip, the shape and arrangement of the coil may be devised. It is necessary to arrange a magnetic body around the coil to adjust the magnetic force distribution.

In the case of performing induction heating using a single coil, the heating pattern generally changes when the transport speed of the metal strip is changed. Therefore, it is difficult to uniformly heat the metal strip in the width direction without depending on the transport speed.

Here, the measurement result of the heating pattern when the metal strip 1 is heated while being conveyed by the single oval coil 2b shown in FIG. 11 is shown in the graph of FIG. 12
In the graph, when the transport speed of the metal strip 1 is 10.7 m / min, a heating pattern showing a substantially uniform temperature distribution over the entire width direction of the metal strip (base material) is obtained as shown by the curve I. Has been. On the other hand, the transport speed is 53.9 per minute.
In the case of m, as shown by the broken line II, the base material temperature greatly changes near both ends in the width direction of the metal strip, and the temperature distribution becomes non-uniform. As described above, in the induction heating using a single coil, even if a uniform heating pattern is obtained at one carrying speed, a uniform heating pattern is not always obtained at other carrying speeds.

The present invention has been made in view of the above circumstances, and provides a technique for easily induction-heating a metal strip in a widthwise direction in a desired heating pattern regardless of the transport speed of the metal strip. With the goal.

[0009]

In order to achieve the above object, according to the induction heating method for a metal strip according to claim 1 of the present invention, an induction heating coil is provided while the metal strip is being conveyed in the longitudinal direction. In the method of induction heating in (1), a method is used in which the heating patterns in the width direction of the metal strip in the case of induction heating with a single coil are sequentially passed through the front faces of the winding surfaces of the plurality of coils.

As described above, according to the induction heating method for a metal strip of the present invention, induction heating is performed by combining a plurality of coils having different heating patterns, which are temperature distributions in the width direction of the metal strip. This makes it possible to easily obtain a desired heating pattern as a combined heating pattern in which heating patterns of individual coils are combined. Moreover, it is possible to reduce the dependency of the combined heating pattern on the transport speed of the metal strip. As a result, the metal strip can be induction-heated in a desired heating pattern even when the transport speed is changed.

The desired heating pattern is not limited to the case where the temperature distribution is uniform in the width direction. For example, the heating pattern may be such that the temperature near both side edges in the width direction is slightly higher than the temperature near the center. Further, in the present invention, the metal strip includes a laminate of resin layers.

According to a second aspect of the present invention, there is provided a method in which the coils have different planar shapes so that the coils have different heating patterns. By doing so, the heating patterns can be easily made different between the coils.

According to a third aspect of the present invention, a magnetic material is arranged in the vicinity of at least one of the coils to make the heating patterns different between the coils. By doing so, the heating patterns can be easily made different between the coils.

According to the fourth aspect of the present invention, the heating pattern is made different between the coils by making the inner diameters of the curved portions at both ends in the longitudinal direction of the coils different from each other. By doing so, the heating patterns can be easily made different between the coils.

According to the fifth aspect of the invention, as the plurality of coils, the heating patterns change in a direction in which the changes in the heating patterns of the other coils are offset when the transport speed of the metal strip is changed. This is a method of using a combination of coils. Thereby, even if the transport speed of the metal strip changes, it is possible to easily suppress the change of the combined heating pattern due to the plurality of coils.

According to a sixth aspect of the present invention, a method is used in which, as the plurality of coils, coils having heating patterns in which the temperature levels in the temperature distribution are inverted from each other are used in combination. In this way, if induction heating is performed by combining the coils whose temperature distribution is reversed, it is possible to easily obtain a uniform combined heating pattern in the width direction.

According to a seventh aspect of the present invention, there is provided an induction heating device for a metal strip, which is a heating device for performing induction heating while transporting the metal strip in the longitudinal direction. Along the line, a plurality of induction heating coils are sequentially arranged so that the orbiting surface of each coil faces the metal strip plate,
The heating patterns in the width direction of the metal strip in the case of induction heating with a single coil are different from each other.

As described above, according to the induction heating device for a metal strip of the present invention, induction heating is performed by combining a plurality of coils having different heating patterns. As a result, it is possible to reduce the dependency of the combined heating pattern obtained by combining the heating patterns of the individual coils with respect to the transport speed of the metal strip. As a result, the metal strip can be induction-heated in a desired heating pattern even when the transport speed is changed.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a metal strip induction heating apparatus and method according to the present invention will be described below with reference to the drawings.

[First Embodiment] First, a first embodiment of the present invention will be described with reference to FIGS. According to the induction heating device for a metal strip of the first embodiment, as shown in FIG. 1, the winding surface of each coil sequentially faces the metal strip 1 along the conveying direction of the metal strip 1. Two induction heating coils 2a and 2b are arranged in the. That is,
On the upstream side in the transport direction, there is arranged a rhomboid coil 2a in which at least one of the four corners facing both side edges of the metal strip is curved. Further, on the downstream side in the transport direction, an oval coil 2b composed of parallel straight portions and curved portions connecting both ends thereof is arranged. Further, a ferrite 30 is arranged near the elliptical coil 2b so as to be parallel to the straight line portion.

In this way, the diamond-shaped coil 2a and the elliptical coil 2b have different planar shapes. Therefore, the heating pattern in the width direction of the metal strip 1 is different between the coils. Here, in the graph of FIG.
Curves I and II show the measurement results of the heating pattern when the metal strip (metal base material) is individually induction-heated by the diamond coil 2a and the elliptical coil 2b. In addition, at the time of this measurement, the metal strip 1 was conveyed at a speed of 10.7 m / min.

As shown by the curve I in the graph, the heating pattern by the diamond-shaped coil 2a has an M-shaped temperature distribution in which the temperature is low at both ends and the center in the width direction. On the contrary,
As shown by the curve II, the heating pattern formed by the oval coil 2b has a W-shaped temperature distribution in which the temperature is high at both ends and the center in the width direction. As described above, in the oval coil 2b in which the ferrite 30 is arranged to adjust the temperature distribution and the diamond-shaped coil 2a, the high and low patterns of temperature in the temperature distribution are reversed.

As a result, the combined heating pattern obtained by combining the heating pattern of the rhomboid coil 2a and the heating pattern of the oval coil 2b has a more uniform temperature distribution in the width direction. Here, in FIG. 2A, curves I and II are shown.
The measurement result of the synthetic heating pattern of the heating pattern shown in FIG. As shown in the curve III, the diamond coil 2a
The combined heating pattern obtained by combining the and oval coils 2b has a more uniform temperature distribution in the width direction.

By the way, the heating pattern of the diamond-shaped coil 2a and the heating pattern of the oval-shaped coil 2b are heated in a direction to cancel the change of the heating pattern of the other coil when the conveying speed of the metal strip 1 is changed. Patterns tend to change. That is, as shown in FIG. 12, when the transport speed of the metal strip is increased, the difference in height of the temperature distribution tends to become larger. For example, in the M-shaped temperature distribution of the rhombus coil 2a and the W-shaped temperature distribution of the oval coil 2b, there is a tendency that the height difference becomes larger when the transport speed is increased. However, if configured to cancel the change in the temperature distribution, even if the transport speed changes,
As a result, a uniform temperature distribution can be maintained.

Here, FIG. 2B shows a combined heating pattern when the transport speed is changed. Curve in graph
I indicates a composite pattern when the transport speed is 10.7 m / min. A broken line II shows a composite pattern when the transport speed is 21.4 m / min. Further, the alternate long and short dash line III shows the combined pattern when the transport speed is 53.9 m / min.
From these curve I, broken line II, and alternate long and short dash line III, it can be seen that a heating pattern having a uniform temperature distribution is obtained regardless of the transport speed.

As described above, according to the first embodiment, by arranging the two coils having different planar shapes sequentially in the flow direction, it is possible to easily realize a uniform synthetic heating pattern, and at the same time, to produce the metal strip. Even when the transport speed of the plate changes, it is possible to suppress the change of the combined heating pattern and maintain a uniform pattern.

Next, with reference to FIG. 3, an example of the arrangement of the coils for inductively heating the aluminum base material and the device configuration in the step of laminating the resin films on both sides of the aluminum base material as the metal strip will be described. . 3A is a plan view of the apparatus, and FIG. 3B is AA of FIG.
FIG.

In the example shown in FIG. 3, rhomboid coils 2a and oval coils 2b are sequentially arranged on both sides of the aluminum base material 1 along the transport path of the aluminum base material 1 to be heated. Here, the coils having the same planar shape are arranged so as to face each other with the aluminum base material 1 interposed therebetween. Therefore, the coils arranged facing each other have the same heating pattern.

The coils 2a and 2b are fixed to a fixed base 4. The fixed base 4 includes a ferrite core and functions as a magnetic field shield plate. Therefore, by providing the fixed base 4, the coupling of the magnetic field with the metal strip plate can be strengthened. The fixed base 4 is not shown in FIG.

Then, two coils 2 are provided on each side.
The aluminum base material 1 induction-heated by a and 2b is conveyed downward in the drawing. Subsequently, the aluminum base material 1 is sandwiched between the resin films 8 extruded from the extrusion die 5. Then, the aluminum base 1 and the resin film 8 are pressure bonded by the laminating roll 7.

FIG. 4 shows an apparatus for arranging the coils 2a and 2b shown in FIG. As shown in FIG. 4, the fixed base 4 is rotated by turning the handle 11.
It can be rotated, for example, within a range of ± 40 ° via the chain 12. As a result, according to the width of the aluminum base material 1, it is possible to easily set the edge heating to be optimal.

Further, in the fixed base 4, the rotation center 15 of the fixed base 4 can be moved in parallel in the width direction of the aluminum base material via the support member 16 by moving the lever 14 left and right. By this parallel movement, the position of the heating range in the width direction is adjusted, and, for example, the center axis of the coil 2 and the center line of the aluminum base material 1 in the width direction are easily aligned,
The aluminum base material 1 can be heated symmetrically. Further, for example, the curved portions at both ends of the long axis of the coils 2a and 2b can be easily overhanged to the outside of the side edges 10 of the aluminum base material 1 by the same degree, and the inner peripheral edges of the curved portions can be more than the side edges 10. Can also be arranged to be located inside. Thereby, the aluminum base material 1 can be heated more uniformly in the width direction.

Second Embodiment Next, a second embodiment of the present invention will be described. Prior to the description of the example of the induction heating device for a metal strip according to the second embodiment, it will be described with reference to FIGS. 5 and 6 that when a ferrite is arranged in the vicinity of the coil, the heating pattern varies depending on the arrangement.

First, FIGS. 5A to 5D show examples of ferrite arrangement patterns in the vicinity of the elliptical coil. Figure 5
(A) shows the case where the ferrite near the coil 2 is not arranged. Further, FIG. 5B shows that the ferrite 3 indicated by “A1” is provided only on the inner side of the orbiting surface of the coil 2.
1, the ferrite 32 shown by "A2" and the ferrite 33 shown by "A3" are arranged. Also, FIG.
(C) is “B” along the outside of the straight part of the coil 2.
The ferrite 34 indicated by and the ferrite 35 indicated by “C” are arranged. Further, (D) of FIG.
The ferrite 32 indicated by "A2" is arranged on the inner side of the orbiting surface of the coil 2, and the ferrite 34 indicated by "B" and the ferrite 35 indicated by "C" are arranged along the outer side of the linear portion of the coil 2. I will show you how.

Further, the graph of FIG. 6 shows the graphs of FIG.
The heating pattern by each coil shown to (D) is shown. That is, as shown by the curve I in the graph, as shown in FIG.
The heating pattern by the coil 2 shown in (1) shows a shallow W shape in which the temperatures at both ends and the central part are high. Further, as shown by the broken line II, the heating pattern by the coil 2 shown in FIG. 5B is flat near the center and has peaks near both ends. Further, as shown by the alternate long and short dash line III, the heating pattern by the coil 2 shown in FIG. 5C has a low peak on both sides and a broad peak near the center. Further, as shown by the chain double-dashed line IV, the heating pattern by the coil 2 shown in FIG. 5 (D) is greatly lowered on both sides and has three peaks near the center.

As described above, the curve I, the broken line II, and the alternate long and short dash line III
From the two-dot chain line IV, it can be seen that when ferrite is arranged near the coil, the heating pattern differs depending on the arrangement.

According to the induction heating device for metal strips of the second embodiment, as shown in FIG. 1, the circumferential surface of each coil faces the metal strip 1 along the transport direction of the metal strip 1. To
Two induction heating coils 2c and 2d having the same planar shape are sequentially arranged. Here, each coil 2
c and 2d are oval coils composed of parallel straight portions and curved portions connecting both ends thereof.

However, in the second embodiment, the heating patterns of the coils 2c and 2d are made different by making the arrangement of the ferrite near the coils 2c and 2d different. That is, in the coil 2 on the upstream side in the transport direction, the ferrite 30 is arranged only inside the winding surface. Further, in the coil 2 on the downstream side, the ferrite 30 is arranged only outside the orbiting surface.

Here, in the graph of FIG. 8, the measurement results of the heating pattern when the metal strips (metal base materials) are individually induction-heated by the coils 2c and 2d are shown by a curve I and a broken line II, respectively.

As shown by the curve I in the graph, the heating pattern by the coil 2c having the ferrite 30 arranged inside shows a temperature peak near both ends in the width direction, and
It has a temperature distribution showing a low temperature in the central portion and both side edges.
On the other hand, as shown by the broken line II, the ferrite 3
The heating pattern by the 0 coil 2d has a shallow W-shaped temperature distribution in which the temperature is high at both ends and the central portion in the width direction. As described above, in the coils 2c and 2d in which the ferrite 30 is arranged and the temperature distribution is adjusted, the high and low patterns of temperature in the temperature distribution are inverted.

As a result, the combined heating pattern obtained by combining the heating patterns of the coils 2c and 2d has a more uniform temperature distribution in the width direction. Here, in FIG. 8, the measurement result of the combined heating pattern of the heating patterns shown by the curve I and the broken line II is shown by a dashed-dotted line III. As shown by the alternate long and short dash line III, the combined heating pattern obtained by combining the coils 2c and 2d has a more uniform temperature distribution in the width direction.

When the transport speed of the metal strip is increased,
Since the height difference of the temperature distribution tends to be larger, the temperature distribution of the coils 2c and 2d also tends to be larger when the conveyance speed is increased. However, if the changes in the temperature distribution are changed in a canceling manner, it is possible to maintain a uniform temperature distribution as a result even if the transport speed changes.

Next, with reference to FIG. 9, an example of the arrangement and apparatus configuration of the coil for induction heating the aluminum base material in the step of laminating the resin film on both sides of the aluminum base material as the metal strip will be described. . FIG. 9A is a plan view of the apparatus, and FIG. 9B is AA of FIG. 3A.
FIG.

In the example shown in FIG. 9, elliptical coils 2c and 2d are sequentially arranged on both sides of the aluminum base material 1 along the conveyance path of the aluminum base material 1 to be heated. Here, coils with the same heating pattern are
The aluminum base materials 1 are arranged so as to face each other with the aluminum base material 1 interposed therebetween.

The coils 2c and 2d are fixed to the fixed base 4. The fixed base 4 includes a ferrite core and functions as a magnetic field shield plate. Therefore, by providing the fixed base 4, the coupling of the magnetic field with the metal strip plate can be strengthened. The fixed base 4 is not shown in FIG. Also, fixed base 4
Can be rotated by the mechanism shown in FIG. 4 as in the first embodiment described above.

Then, two coils 2 are provided on each side.
The aluminum base material 1 induction-heated by c and 2d is conveyed downward in the drawing. Subsequently, the aluminum base material 1 is sandwiched between the resin films 8 extruded from the extrusion die 5. Then, the resin film 8 is pressure-bonded to the aluminum base material 1 by the laminating roll 7.

The induction heating device can perform highly efficient heating in a short time. As a result, the device can be made smaller than a contact roll heating device or the like, so that the device can be arranged immediately before laminating. On the other hand, in the contact roll heating device, the place where the facility is placed is limited, and it may not be possible to place the device just before laminating. In that case, the idling distance becomes long, and it becomes necessary to raise the maximum temperature during heating by the amount of heat released during that time. However, since the induction heating device can be arranged immediately before lamination, it is not necessary to raise the temperature of the heat radiation, and the maximum temperature during heating can be suppressed to a low level. Aluminum etc. softens as the temperature rises. Therefore, the induction heating device can suppress the softening of aluminum, and a material having higher strength can be obtained in the production of the material for a can. As a result, it becomes possible to use a thin material, and the cost can be reduced.

By the way, in the second embodiment, by disposing the ferrite in the vicinity of the elliptical coil, the heating patterns of the coils sequentially arranged along the transport direction of the metal strip are made different, but the same. Even if the coils are shaped and the ferrites are not arranged or arranged in the same pattern, the heating patterns of the coils can be different. For example, the heating patterns can be made different between the coils by making the inner diameters between the curved portions at both ends in the longitudinal direction of the coils sequentially arranged in the flow direction different from each other.

FIG. 10 shows the elliptical coil 2 and its heating pattern. In the lower graph of FIG. 10, the heating pattern when the transport speed is changed is shown by the curve I, the broken line II, and the alternate long and short dash line III. As shown in these graphs, it can be seen that the temperature is constant at points A and B, which face the inner edges of the curved portion 20 at both ends in the major axis 3 direction of the oval coil 2, regardless of the transport speed. Therefore, a desired combined heating pattern can be obtained by vertically arranging a plurality of oval coils 2 such that the positions of the points A and B are different in the width direction.

In the above-described embodiment, the example in which the present invention is configured under a specific condition has been described, but the present invention can be variously modified. For example, in the above-described embodiment, an example in which two coils are sequentially arranged along the transport direction of the metal strip has been described, but in the present invention,
The number of coils is not limited to this. For example, three or more coils may be sequentially arranged in the transport direction to perform induction heating.

Further, in the above-described embodiment, an example of induction heating the metal strip immediately before laminating the resin film has been described. However, the present invention is applicable to the case where the metal strip laminated with the resin film is induction heated. It is also suitable to use. For example, in order to improve the adhesion between the resin film of the laminated plate and the metal plate, reheating may be performed after the lamination. At this time, if heating is performed by induction heating, only the metal strip can be selectively heated, so that the temperature of the interface can be raised as much as necessary without heating the entire laminated resin film. As a result, without damaging the resin film,
Adhesion can be increased.

Further, in the above-described embodiment, an example in which heating patterns of a plurality of coils are combined to realize a uniform combined heating pattern in the width direction has been described. However, in the present invention, the combined heating pattern is uniform. Not limited.
For example, the temperature of the heated metal strip tends to drop faster near the side edges than near the center in the width direction. Therefore, in some cases, it may be preferable to perform heating by induction heating in a heating pattern in which the vicinity of both edges is slightly higher than the vicinity of the center. Even in that case, a desired combined heating pattern can be easily obtained by combining the heating patterns of the plurality of coils.

Further, even if the heating pattern has a non-uniform temperature distribution in the width direction, if the heating patterns of a plurality of coils are combined, the dependence of the transport speed of the metal strip can be reduced. .

Further, in the above-described embodiment, the example of the oval shape and the rhombus shape having the line symmetry with respect to the long axis has been described as the plane shape of the coil, but in the present invention, the plane shape of the coil is Not limited to. For example, a coil having a planar shape that is asymmetric with respect to the long axis may be used.

Further, in the above-described embodiment, an example in which the metal strip is heated by only induction heating has been described, but in the present invention, induction heating may be combined with another heating method.

[0056]

As described above in detail, according to the present invention, induction heating is performed by combining a plurality of coils having different heating patterns. This makes it possible to easily obtain a desired heating pattern as a combined heating pattern in which heating patterns of individual coils are combined.
Moreover, it is possible to reduce the dependency of the combined heating pattern on the transport speed of the metal strip. As a result, the metal strip can be induction-heated in a desired heating pattern even when the transport speed is changed.

The present invention is also suitable for use in heating before lamination when producing a laminated metal strip, and in drying heating during surface treatment.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining the shape and arrangement of a coil for induction heating in a first embodiment.

FIG. 2A is a graph showing a heating pattern of each coil in the first embodiment and a heating pattern in the case of combining two coils, and FIG. 2B is a transportation speed of a metal strip. It is a graph which shows a heating pattern when changing.

3A and 3B are configuration diagrams of an induction heating device for a metal strip according to the first embodiment.

FIG. 4 is an explanatory diagram of a coil rotating mechanism in the metal strip heating device according to the first embodiment.

5A to 5D are diagrams showing a state in which ferrite is arranged in the vicinity of a coil.

FIG. 6 is a graph showing the difference in heating pattern depending on the arrangement of ferrites.

FIG. 7 is a schematic diagram for explaining the shape and arrangement of a coil for induction heating in the second embodiment.

FIG. 8 is a graph showing a heating pattern of an individual coil and a heating pattern when two coils are combined in the second embodiment.

9A and 9B are configuration diagrams of an induction heating device for a metal strip according to a second embodiment.

FIG. 10 is a diagram showing a relationship between a major axis inner diameter of a coil and a heating pattern.

FIG. 11 is a schematic view showing a state of induction heating a metal strip by a conventional single coil.

FIG. 12 is a graph showing changes in the heating pattern when the transport speed of the metal strip is changed.

[Explanation of symbols]

1 metal strip 2, 2a, 2b coil 3 long axis 4 fixed base 5 Extrusion die 6 support rolls 7 Laminating roll 8 resin film 10, 10a Side edge 11 handle 12 chains 13 pulley 14 lever 15 Rotation center of fixed base 16 Connection member 20 curved part 21 outer edge 22 Inner periphery 30, 31, 32, 33, 34, 35 Ferrite

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3K059 AA08 AB19 AC33 AD05 CD09                       CD10                 4K034 AA01 AA08 AA09 BA05 DA04                       DA05 DA06 DB02

Claims (7)

[Claims] 1. When carrying out induction heating with a coil for induction heating while transporting a metal strip in the longitudinal direction, a plurality of coils having different heating patterns in the width direction of the metal strip when induction heating is performed by a single coil. An induction heating method for a metal strip, which comprises sequentially passing the front surface of the orbiting surface. 2. The induction heating method for a metal strip according to claim 1, wherein the heating patterns are made different between the coils by making the plane shapes different between the coils. 3. The induction heating for a metal strip according to claim 1, wherein a heating pattern is made different between the coils by disposing a magnetic material near at least one of the coils. Method. 4. The heating pattern according to claim 1, wherein the coils have different inner diameters between the curved portions at both ends in the longitudinal direction, so that the heating patterns differ between the coils. Induction heating method for metal strip. 5. As the plurality of coils, a combination of coils whose heating patterns are changed in a direction of canceling a change of heating patterns of other coils when changing a conveying speed of the metal strip is used in combination. The induction heating method for a metal strip according to any one of claims 1 to 4, which is characterized in that. 6. The metal strip according to claim 1, wherein, as the plurality of coils, coils having heating patterns in which the temperature levels in the temperature distribution are inverted from each other are used in combination. Induction heating method. 7. An apparatus for inductively heating a metal strip while transporting it in the longitudinal direction, wherein the coil strips are sequentially arranged along the transport direction of the metal strip so that the orbiting surface of each coil faces the metal strip. Induction heating of a metal strip, characterized in that the heating pattern in the width direction of the metal strip when the induction heating is performed by a single coil is different from each other. apparatus.